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KVM: selftests: Add guest_memfd testcase to fault-in on !mmap()'d memory

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Add a guest_memfd testcase to verify that a vCPU can fault-in guest_memfd
memory that supports mmap(), but that is not currently mapped into host
userspace and/or has a userspace address (in the memslot) that points at
something other than the target guest_memfd range.  Mapping guest_memfd
memory into the guest is supposed to operate completely independently from
any userspace mappings.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20250729225455.670324-25-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson
2025-07-29 15:54:55 -07:00
committed by Paolo Bonzini
parent a11d7124b4
commit 42188667be
1 changed files with 64 additions and 0 deletions
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64
tools/testing/selftests/kvm/guest_memfd_test.c
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@@ -13,6 +13,7 @@
#include <linux/bitmap.h>
#include <linux/falloc.h>
#include <linux/sizes.h>
#include <setjmp.h>
#include <signal.h>
#include <sys/mman.h>
@@ -21,6 +22,7 @@
#include "kvm_util.h"
#include "test_util.h"
#include "ucall_common.h"
static void test_file_read_write(int fd)
{
@@ -298,6 +300,66 @@ static void test_guest_memfd(unsigned long vm_type)
kvm_vm_free(vm);
}
static void guest_code(uint8_t *mem, uint64_t size)
{
size_t i;
for (i = 0; i < size; i++)
__GUEST_ASSERT(mem[i] == 0xaa,
"Guest expected 0xaa at offset %lu, got 0x%x", i, mem[i]);
memset(mem, 0xff, size);
GUEST_DONE();
}
static void test_guest_memfd_guest(void)
{
/*
* Skip the first 4gb and slot0. slot0 maps <1gb and is used to back
* the guest's code, stack, and page tables, and low memory contains
* the PCI hole and other MMIO regions that need to be avoided.
*/
const uint64_t gpa = SZ_4G;
const int slot = 1;
struct kvm_vcpu *vcpu;
struct kvm_vm *vm;
uint8_t *mem;
size_t size;
int fd, i;
if (!kvm_has_cap(KVM_CAP_GUEST_MEMFD_MMAP))
return;
vm = __vm_create_shape_with_one_vcpu(VM_SHAPE_DEFAULT, &vcpu, 1, guest_code);
TEST_ASSERT(vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_MMAP),
"Default VM type should always support guest_memfd mmap()");
size = vm->page_size;
fd = vm_create_guest_memfd(vm, size, GUEST_MEMFD_FLAG_MMAP);
vm_set_user_memory_region2(vm, slot, KVM_MEM_GUEST_MEMFD, gpa, size, NULL, fd, 0);
mem = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
TEST_ASSERT(mem != MAP_FAILED, "mmap() on guest_memfd failed");
memset(mem, 0xaa, size);
munmap(mem, size);
virt_pg_map(vm, gpa, gpa);
vcpu_args_set(vcpu, 2, gpa, size);
vcpu_run(vcpu);
TEST_ASSERT_EQ(get_ucall(vcpu, NULL), UCALL_DONE);
mem = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
TEST_ASSERT(mem != MAP_FAILED, "mmap() on guest_memfd failed");
for (i = 0; i < size; i++)
TEST_ASSERT_EQ(mem[i], 0xff);
close(fd);
kvm_vm_free(vm);
}
int main(int argc, char *argv[])
{
unsigned long vm_types, vm_type;
@@ -314,4 +376,6 @@ int main(int argc, char *argv[])
for_each_set_bit(vm_type, &vm_types, BITS_PER_TYPE(vm_types))
test_guest_memfd(vm_type);
test_guest_memfd_guest();
}